High-temperature alloy



United States Patent Ofifice Patented Mar. 29, 1966 3,243,291HIGH-TEMPERATURE ALLOY Clayton D. Dickinson, Port Washington, and SamFriedman, Great Neck, N.Y., assignors to General Telephone andElectronics Laboratories, Inc., a corporation of Delaware No Drawing.Filed Get. 29, 1963, Ser. No. 319,638 4 Claims. (Cl. -176) Thisinvention relates to alloys for use at elevated temperatures and inparticular to tungsten-base alloys containing additions of carbon and areactive material.

Recent developments in aircraft and space vehicles have created a needfor metals which have high strength at elevated temperatures yet remainductile at relatively low temperatures. In addition, these metals mustexhibit high recrystallization temperatures. Known materials are notsatisfactory for many high temperature applications and it is thereforean object of our invention to provide alloys having the requiredcharacteristics.

In the present invention, tungsten-base alloys are provided whichcontain small additions of carbon and reactive metals selected from thegroup consisting of hafnium, zirconium and titanium. These ternaryalloys contain between 0.004 and 0.05 percent carbon and between 0.01and 2.0 percent reactive metal, the balance being tungsten. By varyingthe constituents within the specified ranges the best combination ofmechanical properties and ease of fabricability may be obtained for agiven application.

In particular, at a temperature of 1650 C., ultimate tensile strengthsin the range 25,000 to 73,000 pounds per square inch are exhibited bythe alloys as compared to EXAMPLE I Elemental powders of carbon andtungsten were blended with hafnium hydride to form a uniform mixturewhich was then subjected to a pressure of approximately 50,000 poundsper square inch to form a billet. The billet was next sintered at about2300 C. for approximately minutes to mutually diffuse the differentingredients thereby forrning a solid solution of hafnium in tungsten,the carbon being partitioned between tungsten carbide and a solidsolution of carbon in tungsten. The billet was then fabricated byrolling initialy at l850.C.l950 C. with final rolling at 1550 C. to formsheets having a thickness of approximately 0.040 inch. While a powdermetallurgy process was used in forming the sheets, it shall beunderstood that the alloys may also be consolidated by other processessuch as vacuum arc-casting. Fabrication may be accomplished by othertechniques such as extruding, forging or drawing to produce the desiredwrought form. Measurements of ultimate tensile strength, stress-rupturestrength, recrystallization temperature and ductile-to-brittletransition temperature were carried out for a number of alloys.

The recrystallization temperature was established by determining at whattemperature the fibrous structure of the Wrought alloy completelydisappeared and recrystallization Was essentially complete. Theductile-to-brittle transition temperature was measured by bending awrought sample over a radius four times the thickness of the sheetthrough a angle at several temperatures and determining the minimumtemperature at which deformation occurred without cracking.Characteristics of wrought tungsten-hafnium-carbon alloys of differentcompositions are shown in Table I.

Table I Alloy, percent by weight Ultimate tens. Stress-rupt. in 10Recryst. Ductile-to-brittle strength at l,650 hours at 1,650 O. temp.C.) trans. temperature Ht 0 W C. (p.s.i.) (p.s.i.) 0.)

0. 01 0. 013 Bal. 25, 000 0. 03 0. 017 61, 700 -175 0. 24 0. 004 73, 8000. 53 0. 033 67, 800 125 0. 48 0. 037 66, 200 150-175 0. 49 0. 050 61,500 l. 07 0. 015 68, 500 150 2. 0 0. 015 58, 000

15,000 pounds per square inch for unalloyed tungsten. The temperatureabove which the alloy becomes substantially ductile (thebrittle-to-ductile transition temperature) is equal to or less than thatfor unalloyed tungsten. The high strengths and high recrystallizationtemperatures obtained in the tungsten-reactive metal-carbon alloys aredue to the formation, during fabrication, of a uniformly dispersedreactive metal carbide having particle sizes pre- 65 By contrast, thefollowing values are reported for un- 0 alloyed tungsten:

Ultimate tensile strength at 1650 C. 15,00 pounds per square inch.Recrystallization temperature 1600 C. Ductile-to-brittle transitiontemperature 200 C.

Carbon base alloys containing 0.15 to 1.0 hafnium and 0.015 to 0.035carbon exhibit an optimum combination of ultimate tensile strength,recrystallization temperature, ductile-to-brittle transition temperatureand fabricability.

EXAMPLE II An alloy consisting of tungsten, zirconium, and carbon wasprepared by the method described for the alloy of consistent withdesired mechanical properties have been found most suitable.

As many changes could be made in the above described processes it isintended that all matter contained therein Example I. Table II gives thecharacteristics of various 5 shall be interpreted as illustrative andnot in a limiting compositions of this alloy. sense.

Table 11 Alloy, percent by weight Ultimate tens. Recrystall.Ductile-to-brittle strength at 1,650 temperature transition temp.

C. (p.s.i.) Zr I C W 0. 01 0.015 Bal. 35,000 0. 03 0. 013 70, 800 1, 700125-150 0.11 0. 012 62, 400 1, 850 5125 0.11 0.050 725 0. l3 0. 004 61,100 1, 825 125-150 0. 45 0. 036 69, 600 1, 800 125-150 0. 015 0. 015 64,000

Carbon base alloys containing 0.05 to 0.5 percent zirconium and 0.01 to0.025 percent carbon exhibit a highly desirable combination of ultimatetensile strength, recrystallization temperature, ductile-to-brittletransition temperature and fabricability.

EXAMPLE III An alloy consisting of 0.24 percent titanium, 0.027 percentcarbon with the balance tungsten was prepared by the method of ExampleI. This alloy has the following and 150 C.

From these results it is apparent that our alloys exhibit high strengthat elevated temperatures and are ductile at low temperatures. The alloysalso have high recrystallization temperatures as compared to unalloyedtungsten. For applications where a high melting point is desired, thecomposition containing the minimum alloying ingredients What is claimedis:

1. A tungsten-base alloy consisting essentially of between 0.004 and0.05 percent carbon and between 0.01 and 0.45 percent zirconium, thebalance being tungsten.

2. A tungsten-base alloy consisting essentially of between 0.01 and0.025 percent carbon and between 0.05 and 0.45 percent zirconium, thebalance being tungsten.

3. A tungsten-base alloy consisting essentially of approximately 0.027percent carbon and approximately 0.24 percent titanium, the balancebeing tungsten.

4. A tungsten-base alloy consisting essentially of between 0.004 and0.05 percent carbon and between 0.01 and 0.45 percent zirconium, thebalance being tungsten, said alloy having uniformly dispersed zirconiumcarbide particles distributed therein, the size of said particles beingpredominantly in the range 200 to 1000 Angstroms.

References Cited by the Examiner UNITED STATES PATENTS 3,113,863 12/1963Chang 174 3,116,145 12/1963 Semc'hyshen 75176 3,169,860 2/1965Sernchyshen 75176 DAVID L. RECK, Primary Examiner.

C. N. LOVELL, W. C. TOWNSEND,

Assistant Examiners.

1. A TUNGSTEN-BASE ALLOY CONSISTIN OF ESSENTIALLY OF BETWEEN 0.004 AND0.05 PERCENT CARBON AND BETWEEN 0.01 AND 0.45 PERCENT ZIRCONIUM, THEBALANCE BEING TUNGSTEN.